ELR Ballistics 'Truing' help

[BigBboy25]

I went out today with my .300 Win. Mag. and a bunch of 210 Berger VLD's loaded up to practice a little bit. The rifle shoots very well and I've had great success with this load. The first shot I took was:

1,080 yards
Temp. 76 F
Barometric Pressure 24.48 in Hg
Humidity 13 percent
Angle +3.4 degrees
Latitude 39.45, azimuth 57 degrees
KAC Bullet flight called for 23.25 MOA and no wind. First shot drilled the milk jug.

Next shot was 1,139 yards on one gallon milk jug
Temp 84 F
Barometric Pressure 24.48 in Hg
Humidity 13 percent
Angle +4.0 degrees
Latitude 39.45, azimuth 30 degrees
KAC Bullet flight called for 25.25 MOA and 1.75 MOA for 4 mph full value wind wind. First shot was about 0.75 MOA high, 1/4 MOA right. corrected and fired second round and clipped the right side of the jug and rolled it down the hill.

I decided to try one more shot and it was at 1,555 yards on a little bigger than basketball sized rock.
Temp 84 F
Barometric Pressure 24.48 in Hg
Humidity 13 percent
Angle +5.6 degrees
Latitude 39.45, azimuth 27 degrees
KAC Bullet flight called for 43.25 MOA and 2.5 MOA for 4 mph full value wind wind. First shot was called 3.5 MOA low, good for wind. corrected and fired second round and hit the base of the rock.

I was wondering if anyone had suggestions on how to true my ballistics calculator a bit better. It is spot on out to about 1,100 yards and then I start having errors. I have chronographed my load extensively and I'm confident in my MV and ES is in the 12-15 fps range. I'm getting atmospherics from a Kestrel 4500, measuring range with both a Bushnell 1500 and Leupold RX-IV rangefinder. I have a Leupold VX-III and have checked the tracking on it and have inputted the correction factor into the program. I am also running a single G7 BC of 0.323. If anybody has any ideas on what to try to help bring the output of this program more in line with the results I'm getting? Thanks in advance for any advice.

 

[Topshot]

I am also running a single G7 BC of 0.323. If anybody has any ideas on what to try to help bring the output of this program more in line with the results I'm getting? Thanks in advance for any advice.

There are two things that I would do.

1, Calibrate your scope adjustments over their full range to see if there is any scale factor error in the turret movements.

2. Start using multi G7 B.C. numbers. A single G7 B.C. is quite often no good over the full velocity range that is common out beyond 1200 yards and you will need to use a lower number in this velocity band.

 

[Broz]

What are you using for Muzzle Velocity. What brass , powder and charge weight?


Another thought is , the Rf's you are using have a huge beam divergence. You could very easily be getting bit by this at 1500 plus yards. A misrange off a bush that is closer could be the cuprit. So I suggest you recheck the distance using other methods. Like a board with a few license plates or maybe braking the distance into two shorter shots and add them. Remember to stay in line of sight if possible.

Jeff

 

[lovdasnow]

i'm also curious about banded bc's. I have just been using a single bc but around 1300 and on out to 2200(as far as I've shot) my numbers are a little off.

anyone know what bc numbers shawn is running for the 300gr bergers?

 

[BigBboy25]

I've thought about using banded BC's but haven't tried it yet. I am using 76grs H1000, in Remington cases that are fully prepped, my MV is 2,940 fps on the chronograph at 15 ft and I input 2,970 fps into my program and this got me dialed in very well out to 1,000 on paper.

As far as the rangefinders go I have a cardboard sheet that is about 24"x24" covered with reflective tape that I use. I measured the 1,080 yard with this. For 1,139 yards I ranged the cardboard at 809 and then ranged up to the milk jug from that at 330 yards, I tried to keep everything in strait of a line as possible. I somehow got a range off the rock at 1,555 and was surprised I even got it. There very well could be a ranging error in this one. I checked all the ranges on google earth and 1,080 yard shot measured 1,079 yards, 1,139 was 1,134 on google earth and the 1,555 was 1,547 yards according to google earth.

 

[BigBboy25]

i'm also curious about banded bc's. I have just been using a single bc but around 1300 and on out to 2200(as far as I've shot) my numbers are a little off.

anyone know what bc numbers shawn is running for the 300gr bergers?

I found where Shawn had posted this for the 300 grain Berger:


We have been using the following G1 BC's for quite sometime on the Exbal program.

.818 lower limit 2200 fps
.760 lower limit 1700 fps
.680 lower limit 0 fps

 

[Broz]

For what its worth we only get 2916 from a 28" Broughton 5C with 77 gr of H-1000 and a 210 VLD in that case volume at 4100 ft of altitude. If your inputted velocity is fast it will show up much worse with lower hits past 1000 yards.

I would recheck some other drops at 800, 1000 and 1200 and document them to center group on paper. I would also recheck the 1550 shots and make at least 5 shots on paper wood or steel placed vertivally before I would change too much. I have seen lots of errors caused by estimating a dust ball off a rock at 1500 yards. Remember, the rock could be at an angle, this added to the angle of the bullet path coming in can serve up some bad juju as far as estimating the moa of a miss. Also it is really easy to see the bullet fragments splash into the dirt at the bottom of the rock and call it a low hit. This is why I insist on a vertical target (wood paper or steel) and many groups to work out drops to get a program "spot on".

Also remember if you, your rifle and ammo combined capabilities are 1 moa at 1500 yards a few bullets on the outer edge of this could seem worse than it really is. And a 1 moa combo from a 300 win at 1550 is a pretty darn good one.

Jeff